The American Library Association (ALA) defines a challenge to literature as an attempt by a person or group of people to have literature restricted or removed from a public library or school curriculum. Merely objecting to material is not a challenge without the attempt to remove or restrict access to those materials. The ALA defines a challenge thus:

A challenge is an attempt to remove or restrict materials, based upon the objections of a person or group. A banning is the removal of those materials. Challenges do not simply involve a person expressing a point of view; rather, they are an attempt to remove material from the curriculum or library, thereby restricting the access of others.

According to the ALA, a successful challenge would result in removal of those materials, a form of censorship. However, the ALA agrees that materials may be removed from libraries in appropriate circumstances and Island Trees School District v. Pico suggested that books that are pervasively vulgar may be removed legally.